Vocabulary practice

1. What is steam and how is it produced?

2. What is the purpose of a boiler?

3. What does condense mean? What is the process called, and what is the device used for the process?

4. What is a vacuum?

5. Describe a valve.

6. Describe a piston.

7. Describe a walking beam.

The Creation of Steam Engines

Steam was used to provide power for a kind of mechanical toy in ancient times by an ingenious Greek inventor named Hero of Alexandria. But it was not until the end of the seventeenth century that steam was harnessed for machines that could perform work. The development of these machines is usually regarded as the beginning of the Industrial Revolution. The first steam engines were designed for the practical purpose of pumping water out of mines; the first one to be sold commercially was called the Miner's Friend.

When water is boiled it creates a volume of steam greater than the original amount of water. This greater volume can burst a boiler unless it is released. When the vessel is cooled the steam condenses rapidly so that it returns to its liquid state. The result is a partial vacuum in the vessel that contained the steam. It was this vacuum that was put to work by Thomas Savery and later Thomas Newcomen in the earliest practical steam engines.

In the Savery engine steam from a boiler entered a container. When the container was filled cold water was poured over it there­by creating a partial vacuum that sucked water up into the container. When the container was refilled with steam the water was forced up to a higher level. The valves that controlled the admission of steam to the container as well as the cold water to cause condensation had to be worked by hand on this engine.

The Newcomen engine was an important advance over the Savery engine. The piston was attached by a chain to a walking beam, a heavy lever that worked on the seesaw principle. The other end of the walking beam was attached to a shaft that worked a pump deep in a mine. When the piston was at the top of the steam-filled cylinder, water was shot into the cylinder condensing the steam. Atmospheric pressure forced the piston down, simultaneously raising water from the mine. Steam was allowed to fill the cylinder and the piston moved up to the top, ready for another stroke.

After the Newcomen engine had been in service for a time, it was discovered that the valves that controlled the steam and cold water could be automated—that is, they could be attached to the walking beam in such a way as to turn them on or off by the action of the beam at certain points during the cycle.

Discussion

1. When was steam first used to perform work?

2. Discuss the historical significance of the development of steam engines.

3. What was the first steam engine designed to do?

4. What happens to water when it is boiled?

5. What happens when the vessel in which water has been boiled is cooled? What is the result of this cooling?

6. How did the Savery engine work? How were the valves operated?

7. How did the Newcomen engine improve on the Savery engine?

8. What part did the walking beam play in the Newcomen engine?

9. How were the valves on the Newcomen engine "automated"?

FURTHER DEVELOPMENT OF STEAM ENGINES

Special Terms

Crankshaft: A shaft driving or driven by a crank.

Sun-and-Planet Gears: An arrangement in which a smaller gear (the planet) rotates around a larger gear (the sun).

Safety Valve: A valve that opens automatically when steam or other pressure exceeds a predetermined amount.